Reinforced hoses of thermoplastic materials, such a hose with a nylon core tube, stranded thermoplastic reinforcement of nylon or dacron, and a sheath of polyster or polyurethane have come into widespread use in recent years for applications, such as for conducting refrigerant fluid in automotive air conditioning systems, where conventional reinforced hoses of synthetic rubbers are not suitable because of deterioration by heat, permeability by the fluid conveyed, and other reasons. Permeability by the refrigerant fluid is especially undesirable because of the adverse effect the fluid has on the earth's ozone layer.
Such hoses of reinforced thermoplastics are difficult to couple and seal with reusable hose couplings because of the nature of the thermoplastic core tube materials, particularly when the cost of the couplings must be kept low, as is the case for automotive installations. It is also highly desirable that all parts of such automotive air conditioning system couplings be reusable even though the hose itself may need to be replaced or cut back so the coupling grips on a different section of the hose. In the past reusable couplings for thermoplastic hoses have been provided but have disadvantages that are overcome by the present invention.
For example, U.S. Pat. No. 3,032,358 has parts with complicated machinings, requires separate elastomeric sealing rings, has sharp threads on the nipple and socket that may damage the hose and limit the number of times the joint may be disassembled. U.S. Pat. No. 270,065 is obviously for soft rubber hose and low pressures and would be incapable of gripping and sealing hose of thermoplastic material at working pressures in the range of 200 to 500 PSI and up to 2500 PSI burst strength.